Input data sampling scheme for computer controlled machine tools

ABSTRACT

An apparatus and method for sampling input data to a computer which is controlling the operations of a machine tool. A general purpose digital computer is used to provide servo control signals to the various machine tool slides. The output digital signals of the computer are converted to analog signals by digital to analog converters and fed in the machine tool servo valves which, in turn, control servomotors which, in turn, drive the machine tool slides. Data is sent back to the computer from feedback transducers which are operably connected to the machine tool slides. Means are provided between the feedback transducers and the computers for passing a sampling of the feedback data at periodic intervals. The computer is programmed to request data from the particular feedback device at these intervals. The computer compares this sample of feedback data with the next previous sample of feedback data. This comparison tells the computer the direction, distance, and at what velocity the machine tool slide has moved.

D United States Patent [1 1 [111 Kirkham Dec. 4, 1973 [54] lNPUT DATASAMPLING SCHEME FOR 3,665,168 5/1972 Canfield 235/1501 X COMPUTERCONTROLLED MACHINE 3,578,957 5/197] Gatlin 235/l50.l

TOOLS Primary Examiner-Eugene G. Botz [75] inventor: Edward E. Kirkham,Brookfield, Assistant Examiner jerry Smith Attorney-Cyril M. Hajewski etal.

[73] Assignee: Kearney & Trecker Corporation,

West Allis, Wis. ABSTRACT [22] Filed: Man 31 1972 An apparatus andmethod tor sampling input data to a computer which is controlling theoperations of a ma- [21] Appl. No.: 239,966 chine tool. A generalpurpose digital computer is used to provide servo control signals to thevarious machine Related Apphcauon Data tool slides. The output digitalsignals of the computer [63] g l z of May 1970 are converted to analogsignals by digital to analog 3 an one converters and fed in the machinetool servo valves which, in turn, control servomotors which, in turn,[52] Cl 235/5111 drive the machine tool slides. Data is sent back to thecomputer from feedback transducers which are operag f Gosh ?S? f blyconnected to the machine tool slides. Means are 1 2 /2 603 providedbetween the feedback transducers and the computers for passing asampling of the feedback data at periodic intervals. The computer isprogrammed to [56] References Clted request data from the particularfeedback device at UNITED STATES PATENTS these intervals. The computercompares this sample of 3,611,101 10/1971 Kiffmeyer et a1. 318/603 Xfeedback data with the next previous sample of feedet back data 'Thiscomparison tells the computer the 21 at 343515 1 1 1 rection, distance,and at what velocity the machine e t h 3,465,332 9/1969 Neal 318/636 x Slde as move 3,625,812 12/1971 Gudaz et a1 235/1501 UX 16 Claims, 4Drawing Figures MACH I [\l E 50 45 X-AXIS X-AXIS X-AXIS FEEDBACK SERVO5/ TRANSDUC MOTDR v SE; (00 Y mi s Y-Axi: NA??? 5 $22 V iZi 52 W 476,1 1. V v V r 143 DATA E g/2:5 M Z-Ax|s 2 -Ax1s 5E f BLTT mi W 9 7.1;.W sERvo A a A V T S I 5w|TiHas I VALVE5 IN u ECTlON I Z4'\'AR\THMETICUNIT W l 23 MEMiJR Y UN? l 142 40 25 oNTR0t LiNlT j r 22- OUTPUT 17h? 1B ez 3 D; 3o 20 i g 1 INPUT DATA SAMPLING SCHEME "FOR COMPUTERCONTROLLEDMACHINE TOOLS This application is a continuation of my co-pendingapplication, Ser. No. 035,480, filed May 7, 1970 and now abandoned.

BACKGROUND OF THE INVENTION This invention relates to computercontrolled machine tools and more particularly to an apparatus andmethod for sampling the data sent back to the computer from the variousfeedback transducers.

Before this invention, the computer would send command signalsto themachine tool slide servomechanisms effecting the movement of the slidemembers. Feedback transducers operably connected tothe slide memberswould continuouslysend back feedback data to the computer. Thisfeedbackdata was compared to the command signal until the command signal .andfeedback signal were in agreement at which time the operation of theservomechanism would stop and the positioning of theslide would havebeen effected'by the computer. Whena computer operates in this fashionit is called a real-time operation. The computer-is paralleling dataprocessing with a physical process in such a fashion that the results ofthe data processing are immediately useful to the physical operation.When the computer is being used in a real-time operation it cannot beused to process other needed background programs such as computation andcompiling.

The present invention overcomes the problem of having the computercontinually being tied up in its input/output modeby'taking the computeroff its input- /output mode of operation and permitting it to 'runbackground programs during the time periodsbetween feedback datasamples. This is accomplished by the use of interface apparatus which isused to collect feedback data and pass this larger quantity of data atuniformly spaced apart periodic intervals to the computer.

SUMMARY OF THE INVENTION It is therefore the object of the presentinvention to provide a data samplingapparatus and method which controlsthe sending of feedback data from the feedback transducers to the inputchannels of the computer. The arrangement issuch thateach individualfeedback signal pulse from the data sampling apparatus corresponds to aplurality of individual data input signal pulses from the computer andrepresents a larger increment of movement corresponding to a pluralityof smaller increments of movement conforming in number to the data inputsignal pulses initiating thatparticular total movement and producingthat feedback signal pulse.

According to the present invention, there is provided a machinetoolcomprising a pair of members carried for relative movement, aservomotor connected to effect relative movement between said members, acomputer control system operative to provide output commandsignalsconnectedto actuate the servomotor for effecting predeterminedrelative movement'between the members, a linear'feedback transduceroperative to supply feedback signals to a data sampling means which isconnected between the feedback transducer andthe input channel of thecomputer, and means to effecta' transfer of feedback data to thecomputer from the data sampling means initiated at regular timeintervals. The feedback data'is then processed bythe computer for itsuse in controlling the operation of the machinetool.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a general block schematicshowing the basic components of the computer controlled machine toolsystem;

FIG. 2 is a block schematic diagram of the data sampling unit of FIG..1;

FIG. 3 presentsthe detailed logiccircuit of the X-axis control gateshown in FIG. 2; and,

FIG. 4 presents the detailed logic circuit of theX-axis output gatingmatrix shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1illustrating a block schematic diagram of a computer controlled machinetool system. The machine tool system utilizes data that is recorded ininformationblocks along a punched tape 10.

Each of 'theseblocks of data consists of digital words representinginstructions to the machine tool. These digital words represent thedirection, distance, and rate of movement of the machine tool along theX, Y and Z axes. A tape reader ll'reads therecorded data on the punchedtape 10, in a well-known manner, to provide the operating controlsignals to a control computer 20.

Thecontrol computer v20 can be any suitable form of general digitalcomputer which includes an input section .21, output unit .22, memoryunit 23, arithmetic unit 24, and acontrol unit 25. The control unit 25coordinates the operation of the'rest of the computer. Data stored inthe memory unit23 is supplied under direction of the control unit 25 tothe arithmetic unit 24 for processing and then'returned'to the memoryunit23 to be stored at a location therein. When it is time for someinformation tobe read to the memory unit 23, the control unit 25activates the input section 21 appropriately and sets up a path from theinput section 21 to the proper place in the memory unit 23. Similarly,when an output of information is necessary, the control unit 25 mustactivate the output unit 22 and arrange that the proper information besent from the memory unit or arithmeticunit 24 to the output unit 22.Finally, when anarithmetic operation is to be performed, the controlunit 25 must arrange for the appropriate operands to be transferred fromthe memory unit 23 to the arithmetic unit 24, for the proper operationto be carried out, and the result to be stored back inthe memory unit 23if that is required.

Control computer 20 is the main component of a soft-wire controller.Control computer 20 can provide servo control for the various machinetool slides byclosing the servo loop through the computer using feedbacktransducers and digital to analog converters to drive hydraulic valveswhich, in turn, operate the various axes servomotors.

Theprogram data, that is sent from the tape reader .11 to the controlcomputer 20, is read into the active or buffer portion of the memoryunit 23 of the computer '20 and interpolated into discreet digital pulse.23 until that particular servo movement is completed.

These discreet digital pulse trains are sent from the output device 22along conductors 27, 28 and 29. These signals are converted to analogsignals by the digital to analog (D/A) converters 30, 31 and 32respectively. The analog signals are fed to the machine tool servovalves 35, 36 and 37 by conductors 40,41 and 42 respectively. Servovalve 35 in turn controls a servomotor 45 which drives the X-axismachine tool slide. Servo valve 36 in turn controls a servomotor 46which drives the Y-axis machine tool slide. Servo valve 37 in turncontrols a servomotor 47 which drives the Z-axis machine tool slide.Limit switches 48 are mounted on the machine tool and inform the controlcomputer 20, via conductor 49, of the machine status.

Attached to the machine tool slides are feedback transducers 50, 51 and52 which generate a signal which, when compared to the input signal,verifies that the desired command has been completed. Transducers 50, 51and 52 are of the type which supply a digital signal output. One suchtransducer is the laser interferometer. One such commercially availablelaser interferometer may be the Perkin-Elmer Model INF-1. The outputs ofthe laser interferometer include quadrature square wave signals suitablefor driving standard counters. The quadrature square wave signals fromthe laser feedback transducers 50, 51 and 52 are connected viaconductors 55, 56 and 57 respectively, to a data sampling unit 60. i

As shown in FIG. 2, these quadrature square waves on conductors 55, 56and 57 are connected to a set of direction sensing gates 62, 63 and 64of the three servo loops. The direction sensing gates 62, 63 and 64decode these quadrature signals and determine in which direction themachine axis slides are moving and supply a series of up pulses for onedirection of movement and a series of down pulses for the oppositedirection of travel. Such direction sensing gates are well-known in theart and, therefore, a more detailed description of the internaloperation of direction sensing gates 62, 63 and 64 is not undertakenherein.

Each direction sensing gate contains a synchronizer unit which acts tosave the up and down pulses until a clock pulse, via conductor 66,occurs. The up and down pulses emitted from the direction gatesare'acted on by alternate clock pulses in a manner to be subsequentlydescribed. With the particular Perkin-Elmer interferometer mentionedabove, aup or down pulse, depending on the direction of slide movementis emitted from the direction sensing gate every time the particularslide moves 1.56 microinches. Each of the direction sensing gates 62, 63and 64 is connected to a 3-bit up-down counter 69, 70, 71 respectively.The 3-bit counter diminishes the number of pulses coming from thedirection sensing gates by a factor of 8. The lower frequency pulsetrains are delivered to a control gate 73, 74, 75 respectively; each ofthe lower frequency pulses representing 12.48 microinches of slidemovement. Each of the control gates 73, 74 and 75 acts to add or blockpulses into the -bit up counters 80, 81 and 82 respectively.

The logic circuit of the X-axis control gate 73 is shown in FIG. 3. TheY-axis control gate 74 and the Z- axis control gate 75 are comprised ofcircuits identical to the X-axis control gate. A clock 83, as shown inFIG. 2, supplies a 1,024 kilohertz pulse train to each of the controlgates 73, 74 and 75. The 1,024 kilohertz pulse train is also supplied toa gate timing logic circuit 115, via conductor 116, and to a divide bytwo logic element 117, via conductor 118. Element 117 is a l-bit binarycounter whose output on conductor 119 is a pulse train which isone-halfthe frequency of the 1,024 kilohertz clock pulse train.

As shown in FIG. 3, the 1,024 kilohertz clock signal is supplied viaconductor 84 to a divide by two logic element 85. Element 85 is a 1-bitbinary counter whose output on conductor 86 is a pulse train which isonehalf the frequency of the 1,024 kilohertz clock pulse train. This 512kilohertz pulse train is applied via conductor 86 to AND gate 88. Thedown pulse signals coming from the 3-bitup-down counter 69 is suppliedvia conductor 87 to inverter gate 90. Any down pulses will have beentimed by the synchronizer in the direction sensing gate 62 to coincidewith the 512 kilohertz pulses on conductor 86. The inverted down pulsesignal from inverter gate 90 is supplied to AND gate 88 via conductor91. A logic 1 state on conductor 91 will allow AND gate 88 to pass the512 kilohertz pulse train from the divide by two logic element 85. Theoutput conductor 93 of AND gate 88 is connected to OR gate 94. The 512kilohertz pulse train will be passed by the OR gate 94 and is suppliedvia connector 95 to the X- axis 10-bit up-down counter 80. When the downpulse is passed by inverter gate 90, the state of the output signal ofthis gate goes to the logic state of 0. A logic 0 signal at AND gate 88will act to block the passage of one 512 kilohertz clock pulse. At theend of the down pulse, the logic state of the output of inverter gate 90will change back to a logic 1 state again allowing AND gate 88 to passall of the 512 kilohertz signal pulses. The 1,024 kilohertz clock pulsetrain is also supplied via conductor 97 to AND gate 98. The up pulsesignal coming from the 3-bit up-down counter 69 is supplied viaconductor 89 to AND gate 98. Any up pulses will have been timed by thesynchronizer in the direction sensing gate 62 to coincide with alternatepulses of the 1,024 kilohertz pulse train. An alternate pulse being thepulse that precedes the output pulse of the divide by two logic element85. An up pulse on conductor 89 will enable AND gate 98 to pass oneclock pulse. This clock pulse is supplied to OR gate 94 via conductor101. This pulse will be passed by OR gate 94 and added to the 512kilohertz'pulse traincoming from AND gate 88 via conductor 93 which isalso being passed by OR gate 94. Similarly, the Y-axis control gate 74operates in a like manner and is connected via conductor 76 to theY-axis 10-bit up counter 81. Similarly, the Z-axis control gate 75operates in a like manner and is connected via conductor 77 to theZ-axis l0-bit up counter 82.

The X-axis 10-bit up counter 80 counts up by one when a pulse issupplied via conductor 95. The net count of the counter 80 iscontinuously delivered in binary digit form via conductor 104 to asampling matrix 105. Though conductor 104 is shown as a singleconductor, it will, of course, be understood to include one channel foreach bit sensed. Similarly, the net count of the Y-axis 10-bit upcounter 81 is delivered via conductor 108 to an output gating matrix109. Similarly, the net count of the Z-axis 10-bit up counter 82 isdelivered via conductor 112 to an output gating matrix 113. In thisembodiment of the invention, as shown in FIG. 2, the sampling matrix isshown located within the data sampling unit 60. It is to be understoodthat each of these sampling matrices could be an interface card locatedinside the computer. The interface card plugs into a slot in the inputsection of the computer. Each slot is assigned a fixed address and thecomputer can then communicate with them.

As shown in FIG. 4, the X-axis output gating matrix 105 is comprised ofAND gates numbered 120 to 129. Each AND gate is connected to the outputof one of the binary bits of the 10-bit up counter 80. For example, ifcounter 80 had the net count of 400, there would be a logic 1 signalstanding on conductors 1041, 1041-1 and 104E and a logic 0 signal onconductors 104A, 1048, 104C, 104D, 104F, 1040 and 104J. Another example,if counter 80 had the net count of 15, there would be a logic 1 signalstanding on conductors 104A, 104B, 104C and 104D and a logic 0 signal onconductors 104E, 1041", 1040, 1041-1, 1041 and 104J.

A periodic sample clock pulse C is supplied via conductor 132 to each ofthe AND gates 120 to 129. This periodic sample clock pulse C effects thepassage of the particular net count in the X-axis up counter 80 throughthe AND gates 120 to 129, and via conductor 135 to the input section 21of the control computer 20. The periodic'sample clock pulse C is alsosupplied to the Y-axis sampling matrix 109 and the Z-axis samplingmatrix 113. Similarly, the Y-axis sampling matrix 109 will periodicallypass the net count of the Y-axis up counter 81 via conductor 142 to theinput section 21 of the control computer 20. Similarly, the Z-axissampling matrix 113 will periodically pass the net count of the Z-axisup counter 82 via conductor 143 to the input section 21 of the controlcomputer 20. The control computer 'will compare the outputs of, thesampling matrices 105, 109 and l l3 with the output of a referencel0-bit up counter 149. V I l As shown in FIG. 2, the 512 kilohertz pulsetrain from the divide by two logic element 117 is supplied via conductor119 to the reference counter 149. The output of the reference counter149 is supplied via conductor 150 tothe input section 21 of the controlcomputer 20. Though conductor 150 is shown as a single conductor, itwill, of course, be understood to include one channel for each of theten bits of the reference up counter 149. Whenthere are no up or downpulses being fed into the various control gates 73, 74 and 75, theirrespective up counters 80, 81 and 82 will count in step with thereference counter 149. For example, let us assume we start operating andboth the X-axis up counter 80 and the reference up counter 149 register0 counts. The 512 kilohertz pulse trains on conductors 95 and 119 willcount up the X-axis and reference counters 80 and 149 respectively, inunison. Every L953 microseconds another count will be added to each ofthe up counters 80 and 149. After a period of 976 microseconds therewould be a count of 500 in both the X-axis up counter 80 and thereference up counter 149. Now, let us assume that during the next 976microseconds time period there are 8' down pulses emitted from theX-axis sensing gate 62 indicating that the X-axis slide moved 12.48microinches in a particular direction. Eight down pulses into the 3-bitup-down counter 69 will result in one pulse out on conductor 87,representing the 12.48 microinches of slide movement. As representedearlier, a pulse on conductor 87 will effect the blocking of one of the512 kilohertz pulses being supplied on conductor 86 resulting in oneless pulse being supplied on conductor 93, and consequently, one lesspulse being supplied on conductor 95, to the X-axis up counter 80. Nowthe count in reference counter 149 will be 1000 while the count in theX-axis up counter will be 999, indicating that the X- axis slide moved12.48 microinches in a particular direction.

Now let us assume that another period of 976 microseconds passes. The512 kilohertz pulse train supplied on conductor 119 to the reference upcounter 149 will have advanced that'counter another 500 counts, so itwill now register 476 counts. As we added the 500 new counts toreference up counter 149, the first 23 counts advanced the counter toits top count value of 1,023. The next pulse resets the referencecounter to zero and the remaining 476 pulses were counted in bringingthe reference up counter 149 to its present 476 count position. Now letus assume that during this 976 microsecond period there are 24 up pulsesemitted from the X- axis sensing gate 62 indicating that the X-axisslide moved 37.44 microinches in a direction opposite to the particulardirection assumed above. Twenty-four up pulses into the 3-bit up-downcounter 69 will result in three pulses out on conductor 89, representing37.44 microinches of slide movement. As represented earlier, threepulses on conductor 89 will effect the addition of three pulses to the512 kilohertz pulse train on conductor 93 resulting in three additionalpulses being supplied on conductor 95 to the X-axis up counter 80. Nowthe count in the reference counter will be 476 while the count in X-axisup counter will have advanced from 999 to 478, indicating that theX-axis slide has moved 37.44 microinches in an opposite direction sincethe last time we looked at the counts in the X-axis up counter 80 andthe reference up counter 149.

The control computer 20 will periodically check the number of counts ina particular axis up counter and compares this count with the count thatis in the reference up counter 149. The difference between the count inthe axis up counter and the count in the reference up counter 149 tellsthe control computer 20 how far that particular axis slide moved and inwhat direction.

The periodic sample pulse C is supplied by the gate timing logic circuit115. As mentioned before, the 1 ,024 kilohertz pulse train from clock 83is supplied via conductor 116 to the gate timing logic circuit 115. Thegate timing logic circuit changes the 1,024 kilohertz pulse train into aplurality of lower frequency pulse signals. The circuiting of such agate timing logic circuit is well-known in the art and thus need not bedescribed here.

The desired feedback data sampling rate, that is the frequency of pulseC, is determined in part by taking into consideration the maximumfrequency of the pulse train originating from. the laser interferometerfeedback transducers 50, 51 and 52. With the particular Perkin-Elmerinterferometer mentioned above, a pulse is emitted from the directionsensing gates 62, 63 and 64 every time the particular axis slide moves1.56 microinches. Let us assume that it is desired to provide for a.maximum slide speed of 4.68 inches per second. Therefore, the maximumpulse frequency emitted by the direction sensing gates 62, 63 and 64would be 3 megahertz. The 3-bit counters 69, 70 and 71 will diminishthis pulse frequency by a factor of 8 to 375 kilohertz. The 10-bit upcountrs can handle 1,023 pulses before reverting back to their zerocount state. if we did not sample often enough when we got to the topslide speed, and the l0-bit counter recorded more than 512 pulses, wewould not know whether that counter was counted up or counted down inits relationship withthe reference counter 149. In other words, we wouldnot know whether 512 or more pulses were being added to the pulse trainleaving the control gate, or if 512 or more pulses of the pulse trainwere being blocked by the control gate. Therefore, at top slide speed wewould need to sampe the data within the X- axis up register 80, Y-axisup register 81 and Z-axis up register 82 every millisecond or less. Ofcourse, when the machine tool slides are not moving at top speed, theirfeedback data can be sampled at a less frequent rate.

Control computer 20, through its program instructions, controls thetransfer of the data from the X-axis up register 80, Y-axis up register81, Z-axis up register 82, and the reference up counter 149, to itsinput section 21. The control computer 20 compares the differencebetween one feedback data sample and the next previous feedback datasample producing a result represented by a digital count indicative ofthe error between the commanded slide position and its actual positionat the time of the feedback data sample. If the slide movement calledfor by the tape 10 is a distance long enough to span a number of datasamples, the sampled data will also be indicative of the slide velocity.

Although the illustrative embodiment of the inven tion has beendescribed in considerable detail for the purpose of disclosing apractical operative structure whereby the invention may be practicedadvantageously, it is to be understood that the particular apparatusdescribed is intended to be illustrative only and that the novelcharacteristics of the invention'may be incorporated in other structuralforms without departing from the spirit and scope of the invention asdefined in the subjoined claims.

The principles of this invention having now been fully explained inconnection with the foregoing description, I hereby claim as myinvention:

1. In a computer controlled machine tool system;

a pair of mechanically interconnected members carried for movementrelative to one another;

a position transducer operatively coupled to the machine tool members toprovide a feedback signal indicating the movement of said membersrelative to each other;

a power drive means connected to effect relative movement between saidmembers;

a source of data for initiating input signal pulses;

a computer programmed to produce command signals initiated by said datasource for said power drive means; and t sampling means connectedbetween said position transducer and said computer operable to so passfeedback signals periodically to said computer that each feedback signalequals a plurality of command signal pulses, whereby the computercompares the sampled feedback data with the next previous sampledfeedback data for producing a signal proportional to the relativemovement of said members from a previous position.

2. A computer controlled machine tool system according to claim 1,wherein said position transducer is operative to indicate changes inposition by providing a direct source of digital signal pulses.

3. A machine tool according to claim 2 wherein said transducer is alaser interferometer.

4. In a machine tool having a servo driven movable slide member andprovided with a data source and computer control for producing commandsignals from said data source to the servo drive for effecting the de- 5sired movement of the slide member;

means responsive to the movement of said slide member for producingfeedback signals representative of increments of movement of said slidemember; means for generating a plurality of periodic signals;

and data sampling means connected to receive said feedback signals andbeing responsive to said periodic signals applied thereto for passingthe spaced apart feedback signals to said computer for computing thedifference between said feedback signal sample and the next previousfeedback sample and producing a digital count representing the errorbetween the commanded slide position and its actual position at the timeof the feedback data sample. 5. A method of sampling the input datasupplied to a computer which is controlling the operation of a pluralityof machine tool slide members, comprising the steps of:

ducer which is coupled to the machine tool members and is indicative ofincrements of relative movement of said members; and

sampling the feedback pulses periodically at intervals uniformly spacedapart in time and supplying said sampled feedback pulses to saidcomputer, and

with the sampled feedback pulses having a value proportional to thedirection and distance of relative movement between said machine toolmembers.

6. A method of sampling the input data signal pulses from a sourcesupplied to a computer operatively connected to control the operation ofa plurality of machine tool slide members for moving said members atotal number of increments of movement corresponding in number to thetotal number of input signal pulses comprising the steps of:

generating feedbacksignal pulses from a position transducer which iscoupled to the machine tool members and is indicative of increments ofrelative movement between said members; and

sampling the feedback signal pulses at uniformly spaced apart intervalsof movement and supplying the sampled feedback pulse to said computer ina manner that each sampled feedback pulse is so spaced apart relative tothe other feedback pulses as to have a value proportional to the totalaccumulated incremental distance of relative movement between saidmachine tool members.

7. In a computer controlled machine tool;

a pair of mechanically interconnected members carried for movementrelative to one another;

a position transducer operatively coupled between the machine toolmembers to provide a feedback signal indicating the movement of one ofsaid members relative to the other;

power drive means connected to effect relative movement between saidmembers;

means for initiating data signals;

a computer programmed to produce command signals for controlling saidpower drive means, said computer being operable to transmit signalsinitigenerating feedback pulses from a position transated by said meansto actuate said power drive means to effect movement between saidmembers; and

sampling means connected in the return path between said positiontransducer and said computer operable to pass feedback signals from saidtransducer periodically to said computer, said sampling means beingoperative to space said feedback signals uniformly farther apart in timein a manner that each feedback signal corresponds to a plurality ofindividual data signals from said computer,

whereby the computer compares the sampled feedback data with the nextprevious sampled feedback data for producing a signal proportional tothe relative movement of said members from a previous position. 7

8. In a computer controlled machine tool system;

a machine and a member carried thereby for relative rectilinearmovement;

power drive means to move said member;

a source for initiating input data signals;

computer means programmed to supply data signals initiated by said datasource to operate said power drive means and being simultaneouslyprogrammed to receive return feedback signals at uniformly spaced aparttime periods in a manner that each feedback signal equals plural inputsignals, said computer means being operative to transmit data signalsinitiated by said source in accordance with the program established bysaid computer means;

a transducer actuated by movement of said machine member and operativeto produce feedback signals timed to coincide with the input signalsfrom said computer means; and

sampling means operatively interconnected between said transducer andsaid computer, said sampling means being adapted to accumulate signalsin groups representing corresponding successive increments of movementof said member and pass such signals to said computer at spaced aparttime intervals.

9. In a machine having a member carried for relative rectilinearmovement and a power drive connected to selectively move said member;

signal means for initiating data input signals;

computer means prorammed to dynamically transmit data signals initiatedby said signal means to actuate power drive to move said member;

a transducer actuated by movement of said member operative to providefeedback signals indicating positional movement of said member; and

a data sampler operative to accumulate a plurality of feedback signalsfrom said transducer and connected to transmit resultantly fewerfeedback signals to said controller at uniformly-spaced timeiintervals.

10. in a machine tool having a frame and a member supported by saidframe for movement;

a source of power connected to actuate said movable member in itsmovement;

a source of information furnishing data which specifies the desiredmovement of said movable member;

monitoring means connected to produce data indicating the actualmovement of said member as it is being actuated by said source of power;

comparing means connected to compare the data from said monitoring meansagainst the data furnished by said source of information for producingthe desired control to meet the requirements specified by said source ofinformation; and

sampling means connected to periodically pass the information from saidmonitoring means to said comparing means so that the information istransmitted to said comparing means at spaced intervals of time.

11. A machine tool according to claim 10 wherein said monitoring meansis a transducer connected to produce feedback information indicating theactual movement of said member.

12. A machine tool according to claim 10 wherein said comparing means isa digital computer and said sampling means passes the information fromsaid monitoring means to said computer at spaced intervals of time inorder to free said computer for other functions during such timeintervals.

13. A machine tool according to claim 12 wherein said monitoringv meansis a transducer connected to produce feedback information indicating theactual movement of said member and said sampling means passes suchinformation to said computer for producing the desired control of saidmovable member.

14. A machine tool according to claim 10 wherein said sampling meanscomprises:

a register connected to receive the information from said monitoringmeans and register the movement of said movable member as it occurs;

anAND gate for each bit of said register, each of said AND gates havingan input connected to its associated bit in said register;

a pulse generator for producing electrical pulses at a specificfrequency connected to the input side of each of said AND gates; and

means connecting the outputs of each of said AND gates to said comparingmeans so that each time a pulse is produced by said pulse means, saidAND gates will pass the information from said register to said comparingmeans to produce the desired regulation of said movable member.

15. In a control for regulating the function of a machine tool;

a source of information supplying data which defines the functions to beperformed by the machine tool;

a computer connected to receive the data from said source ofinformation;

monitoring means for each of said functions for producing data toindicate the status of each function as it is being performed;

comparing means in said computer for comparing the information from saidmonitoring means with the stored data from said source of informationfor producing the desired control to meet the requirements specified bysaid source of information; and

sampling means connected to periodically pass the information from themonitoring means of a particular function to said comparing means atspaced intervals of time in order to free said computer for regulatingother functions during such time intervals.

16. A machine tool accordng to claim 15 wherein said sampling meanscomprises:

an AND gate;

said comparing means so that each time a pulse is produced by said pulsemeans, said AND gate will pass the information from said monitoringmeans to said comparing means to produce the desired regulation of thefunction. I

1. In a computer controlled machine tool system; a pair of mechanicallyinterconnected members carried for movement relative to one another; aposition transducer operatively coupled to the machine tool members toprovide a feedback signal indicating the movement of said membersrelative to each other; a power drive means connected to effect relativemovement between said members; a source of data for initiating inputsignal pulses; a computer programmed to produce command signalsinitiated by said data source for said power drive means; and samplingmeans connected between said position transducer and said computeroperable to so pass feedback signals periodically to said computer thateach feedback signal equals a plurality of command signal pulses,whereby the computer compares the sampled feedback data with the nextprevious sampled feedback data for producing a signal proportional tothe relative movement of said members from a previous position.
 2. Acomputer controlled machine tool system according to claim 1, whereinsaid position transducer is operative to indicate changes in position byproviding a direct source of digital signal pulses.
 3. A machine toolaccording to claim 2 wherein said transducer is a laser interferometer.4. In a machine tool having a servo driven movable slide member andprovided with a data source and computer control for producing commandsignals from said data source to the servo drive for effecting thedesired movement of the slide member; means responsive to the movementof said slide member for producing feedback signals representative ofincrements of movement of said slide member; means for generating aplurality of periodic signals; and data sampling means connected toreceive said feedback signals and being responsive to said periodicsignals applied thereto for passing the spaced apart feedback signals tosaid computer for computing the difference between said feedback signalsample and the next previous feedback sample and producing a digitalcount representing the error between the commanded slide position andits actual position at the time of the feedback data sample.
 5. A methodof sampling the input data supplied to a computer which is controllingthe operation of a plurality of machine tool slide members, comprisingthe steps of: generating feedback pulses from a position transducerwhich is coupled to the machine tool members and is indicative ofincrements of relative movement of said members; and sampling thefeedback pulses periodically at intervals uniformly spaced apart in timeand supplying said sampled feedback pulses to said computer, and withthe sampled feedback pulses having a value proportional to the directionand distance of relative movement between said machine tool members. 6.A method of sampling the input data signal pulses from a source suppliedto a computer operatively connected to control the operation of aplurality of machine tool slide members for moving said members a totalnumber of increments of movement corresponding in number to the totalnumber of input signal pulses comprising the steps of: generatingfeedback signal pulses from a position transducer which is coupled tothe machine tool members and is indicative of increments of Relativemovement between said members; and sampling the feedback signal pulsesat uniformly spaced apart intervals of movement and supplying thesampled feedback pulse to said computer in a manner that each sampledfeedback pulse is so spaced apart relative to the other feedback pulsesas to have a value proportional to the total accumulated incrementaldistance of relative movement between said machine tool members.
 7. In acomputer controlled machine tool; a pair of mechanically interconnectedmembers carried for movement relative to one another; a positiontransducer operatively coupled between the machine tool members toprovide a feedback signal indicating the movement of one of said membersrelative to the other; power drive means connected to effect relativemovement between said members; means for initiating data signals; acomputer programmed to produce command signals for controlling saidpower drive means, said computer being operable to transmit signalsinitiated by said means to actuate said power drive means to effectmovement between said members; and sampling means connected in thereturn path between said position transducer and said computer operableto pass feedback signals from said transducer periodically to saidcomputer, said sampling means being operative to space said feedbacksignals uniformly farther apart in time in a manner that each feedbacksignal corresponds to a plurality of individual data signals from saidcomputer, whereby the computer compares the sampled feedback data withthe next previous sampled feedback data for producing a signalproportional to the relative movement of said members from a previousposition.
 8. In a computer controlled machine tool system; a machine anda member carried thereby for relative rectilinear movement; power drivemeans to move said member; a source for initiating input data signals;computer means programmed to supply data signals initiated by said datasource to operate said power drive means and being simultaneouslyprogrammed to receive return feedback signals at uniformly spaced aparttime periods in a manner that each feedback signal equals plural inputsignals, said computer means being operative to transmit data signalsinitiated by said source in accordance with the program established bysaid computer means; a transducer actuated by movement of said machinemember and operative to produce feedback signals timed to coincide withthe input signals from said computer means; and sampling meansoperatively interconnected between said transducer and said computer,said sampling means being adapted to accumulate signals in groupsrepresenting corresponding successive increments of movement of saidmember and pass such signals to said computer at spaced apart timeintervals.
 9. In a machine having a member carried for relativerectilinear movement and a power drive connected to selectively movesaid member; signal means for initiating data input signals; computermeans prorammed to dynamically transmit data signals initiated by saidsignal means to actuate power drive to move said member; a transduceractuated by movement of said member operative to provide feedbacksignals indicating positional movement of said member; and a datasampler operative to accumulate a plurality of feedback signals fromsaid transducer and connected to transmit resultantly fewer feedbacksignals to said controller at uniformly spaced time intervals.
 10. In amachine tool having a frame and a member supported by said frame formovement; a source of power connected to actuate said movable member inits movement; a source of information furnishing data which specifiesthe desired movement of said movable member; monitoring means connectedto produce data indicating the actual movement of said member as it isbeing actuated by said source of power; comparing means connected tocompare the data from said monitOring means against the data furnishedby said source of information for producing the desired control to meetthe requirements specified by said source of information; and samplingmeans connected to periodically pass the information from saidmonitoring means to said comparing means so that the information istransmitted to said comparing means at spaced intervals of time.
 11. Amachine tool according to claim 10 wherein said monitoring means is atransducer connected to produce feedback information indicating theactual movement of said member.
 12. A machine tool according to claim 10wherein said comparing means is a digital computer and said samplingmeans passes the information from said monitoring means to said computerat spaced intervals of time in order to free said computer for otherfunctions during such time intervals.
 13. A machine tool according toclaim 12 wherein said monitoring means is a transducer connected toproduce feedback information indicating the actual movement of saidmember and said sampling means passes such information to said computerfor producing the desired control of said movable member.
 14. A machinetool according to claim 10 wherein said sampling means comprises: aregister connected to receive the information from said monitoring meansand register the movement of said movable member as it occurs; an ANDgate for each bit of said register, each of said AND gates having aninput connected to its associated bit in said register; a pulsegenerator for producing electrical pulses at a specific frequencyconnected to the input side of each of said AND gates; and meansconnecting the outputs of each of said AND gates to said comparing meansso that each time a pulse is produced by said pulse means, said ANDgates will pass the information from said register to said comparingmeans to produce the desired regulation of said movable member.
 15. In acontrol for regulating the function of a machine tool; a source ofinformation supplying data which defines the functions to be performedby the machine tool; a computer connected to receive the data from saidsource of information; monitoring means for each of said functions forproducing data to indicate the status of each function as it is beingperformed; comparing means in said computer for comparing theinformation from said monitoring means with the stored data from saidsource of information for producing the desired control to meet therequirements specified by said source of information; and sampling meansconnected to periodically pass the information from the monitoring meansof a particular function to said comparing means at spaced intervals oftime in order to free said computer for regulating other functionsduring such time intervals.
 16. A machine tool accordng to claim 15wherein said sampling means comprises: an AND gate; a connection fromsaid monitoring means to an input of said AND gate; a pulse generatorfor producing electrical pulses at a specific frequency connected to theinput side of said AND gate; and means connecting the output of said ANDgate to said comparing means so that each time a pulse is produced bysaid pulse means, said AND gate will pass the information from saidmonitoring means to said comparing means to produce the desiredregulation of the function.